The images of the tissues of patients in medical radiographs are prepared by using a photographic material (a silver halide photographic material) comprising a transparent support having at least one light-sensitive silver halide emulsion layer coated thereon, and recording an X-ray transmitted pattern on the silver halide photographic material. The X-ray transmitted pattern can be recorded by using the silver halide photographic material alone. However, since it is not desirable that the human body is exposed to a large dose of a radiation, X-ray photographing is usually conducted by combining the silver halide photographic material with a radiographic intensifying screen. The radiographic intensifying screen comprises a support having a phosphor layer provided on the surface thereof. X-rays are absorbed by the phosphor layer and converted into visible light having high light sensitivity to the photographic material. Hence, the use of the radiographic intensifying screen greatly improves the sensitivity of X-ray photographing systems.
As a method for further improving the sensitivity in the X-ray photographing systems, there has been developed a method wherein a light-sensitive material having photographic emulsion layers on both sides thereof, that is, a silver halide photographic material comprising a support having silver halide photographic emulsion layers on the front side thereof as well as on the back side thereof (i.e., on the opposite side of the front side) is put between radiographic intensifying screens (sometimes hereinafter referred to simply as intensifying screen) and subjected to X-ray photographing. This method is usually applied to X-ray photographing at present. This method is developed because the sufficient absorbed dose of X-rays can not be achieved by the use of only a sheet of the intensifying screen. Namely, even when the amount of the phosphor used in a sheet of the intensifying screen is increased to increase the absorbed dose of X-rays, visible light into which X-rays are converted within the phosphor layer having an increased thickness is scattered and reflected within the phosphor layer and, as a result, visible light which is emitted from the intensifying screen and is incident on the photographic material contacted with the intensifying screen is greatly made out-of-focus. Further, visible light emitted from the depth of the phosphor layer can be come out of the depth with difficulty. Accordingly, even when the amount of the phosphor layer is unnecessarily increased, effective visible light emitted from the intensifying screen is not increased. The X-ray photographing method using two sheets of the intensifying screens having an appropriate thickness has an advantage in that the absorbed dose of X-rays can be increased on the whole, and visible light into which X-rays are effectively converted can be emitted from the intensifying screens.
Studies have been continuously made to find out X-ray photographing systems having excellent balance between the image quality and the sensitivity. For example, there has been developed a combination of a blue light emitting intensifying screen having calcium tungstate phosphor layer with a silver halide photographic material which was not spectrally sensitized (e.g., a combination of High Screen standard with RX; both being trade names of Fuji Photo Film Co., Ltd.). Further, a combination of a green light emitting intensifying screen having a terbium activated rare earth element oxysulfide phosphor layer with an ortho spectrally sensitized silver halide photographic material (e.g., a combination of GRENEX with RXO; both being trade names of Fuji Photo Film Co., Ltd.) has been used in recent years. Both the sensitivity and the image quality have been improved.
The silver halide photographic material having photographic emulsion layers on both sides thereof has a problem in that the image quality is liable to be deteriorated by cross over light. The cross over light refers to visible light which is emitted from each of the intensifying screens arranged on both sides of the photographic material, transmitted through the support (usually a thick support of 170 to 180 .mu.m is usually used) of the photographic material to the opposite sensitive layer thereto and deteriorates the image quality (particularly sharpness).
Various methods have been developed to reduce the above-described cross over light. For example, U.S. Pat. Nos. 4,425,425 and 4,425,426 disclose that spectrally sensitized tabular grain emulsions having a high aspect ratio are used as light-sensitive silver halide photographic emulsions, whereby cross over light can be reduced to 15 to 22%. Further, U.S. Pat. No. 4,803,150 discloses that a microcrystalline dye layer which can be decolorized by development processing is provided between the support of the silver halide photographic material and the light-sensitive layer thereof, whereby cross over light can be reduced to 10% or below.
However, a large amount of the dye is required to make cross over light zero, and the dye is left behind after development processing. Namely, there are caused problems that a residual color is formed, and the layer strength of the photographic material is lowered by adding a large amount of the dye. It is difficult that the well-balanced properties between the image quality and the layer strength can be obtained.
On the other hand, the photographic material having a backing layer, that is, one side photographic material does substantially not suffer from cross over light, that is, cross over light is substantially zero. Accordingly, it is necessary that studies are made on the photographic material having a backing layer to improve the sensitivity and the image quality.